Light source device and projection-type display apparatus

ABSTRACT

A light source device includes: blue, green, and red laser light sources; a first retardation plate that controls polarization of blue laser light emitted from the blue laser light source; a polarizing beam splitter that separates the blue laser light whose polarization is controlled by the first retardation plate into a first blue laser light and a second laser light; a second retardation plate that controls polarization of the second blue laser light separated by the polarizing beam splitter; a fluorescent plate that is excited by the first blue laser light separated by the polarizing beam splitter and emits fluorescent light including a green component and a red component; a first dichroic mirror that combines the second blue laser light whose polarization is controlled by the second retardation plate and light emitted from the green and red laser light sources, to generate combined laser light; a dynamic diffuser plate that diffuses the combined laser light combined by the first dichroic mirror to generate diffused laser light; and a second dichroic mirror that combines the diffused laser light diffused by the dynamic diffuser plate and the fluorescent light emitted from the fluorescent plate.

TECHNICAL FIELD

The present disclosure relates to a light source device and aprojection-type display apparatus including the light source device.

BACKGROUND ART

As a light source for a projection-type display apparatus using an imageforming element such as a mirror-deflection-type digital micromirrordevice (DMD) or a liquid crystal panel, there are disclosed many lightsource devices using a solid-state light source such as a semiconductorlaser or a light emitting diode, which is long life. Among them, thereis disclosed a light source device having a wide color gamut and highefficiency using solid-state light sources of blue, green, and red (seePTL 1).

CITATION LIST Patent Literature

PTL 1: Unexamined Japanese Patent Publication No. H6-208089

SUMMARY OF THE INVENTION

The present disclosure provides a light source device and aprojection-type display apparatus using the light source device. In thelight source device, solid-state light sources of blue, green, and redare used and speckle noise and minute luminance unevenness areeliminated, and at the same time, the light source device has a widecolor gamut and is small in size.

A light source device of the present disclosure includes: a blue laserlight source; a green laser light source; a red laser light source; afirst retardation plate that controls polarization of blue laser lightemitted from the blue laser light source; a polarizing beam splitterthat separates the blue laser light whose polarization is controlled bythe first retardation plate into a first blue laser light and a secondlaser light; a second retardation plate that controls polarization ofthe second blue laser light separated by the polarizing beam splitter; afluorescent plate that is excited by the first blue laser lightseparated by the polarizing beam splitter and emits fluorescent lightincluding a green component and a red component; a first dichroic mirrorthat combines the second blue laser light whose polarization iscontrolled by the second retardation plate, green laser light emittedfrom the green laser light source, and red laser light emitted from thered laser light source to generate combined laser light; a dynamicdiffuser plate that diffuses the combined laser light combined by thefirst dichroic mirror to generate diffused laser light; and a seconddichroic mirror that combines the diffused laser light combined by thedynamic diffuser plate and the fluorescent light emitted from thefluorescent plate.

According to the present disclosure, blue projection light and blueexcitation light are obtained from the same blue laser light source byusing a retardation plate and the polarizing beam splitter, it istherefore possible to downsize the blue laser light source.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 is a configuration diagram of a light source device according toa first exemplary embodiment of the present disclosure.

FIG. 2 is a diagram illustrating spectral transmittance characteristicsof a second dichroic mirror according to the first exemplary embodiment.

FIG. 3 is a diagram showing emission spectrum characteristics offluorescent light.

FIG. 4 is a configuration diagram of a projection-type display apparatusaccording to a second exemplary embodiment of the present disclosure.

FIG. 5 is a configuration diagram of a projection-type display apparatusaccording to a third exemplary embodiment of the present disclosure.

DESCRIPTION OF EMBODIMENTS

Hereinafter, exemplary embodiments for carrying out the presentdisclosure will be described with reference to the drawings.

First Exemplary Embodiment

FIG. 1 is a configuration diagram of light source device 53 according toa first exemplary embodiment of the present disclosure.

Light source device 53 includes blue laser light source 22, green laserlight source 29, and red laser light source 34. Blue laser light source22 includes collimating lens array 21 and blue semiconductor lasersubstrate 20 on which a plurality of blue semiconductor laser elementsare arranged. Green laser light source 29 includes collimating lensarray 28 and green semiconductor laser substrate 27 on which a pluralityof green semiconductor laser elements are arranged. Red laser lightsource 34 includes collimating lens array 33 and red semiconductor lasersubstrate 32 on which a plurality of red semiconductor laser elementsare arranged. Heat sinks 23, 30, 35 are respectively attached to bluelaser light source 22, green laser light source 29, and red laser lightsource 34.

In addition, light source device 53 includes: first retardation plate 24that is a half-wavelength plate; flat plate-shaped polarization beamsplitter 25 that is a polarizing beam splitter; second retardation plate26 that is a half-wavelength plate; blue-reflecting dichroic mirror 31;red-reflecting dichroic mirror 36; condenser lenses 37, 43, 47, 48;diffuser plates 38, 44; reflecting mirror 39; rotary diffuser plate 42that is a dynamic diffuser plate including circular diffuser plate 40and motor 41; second dichroic mirror 46; blue transmission filter 45;and fluorescent plate 52 including motor 51 and aluminum substrate 50 onwhich a reflection film and phosphor layer 49 are disposed.

The drawing shows: polarization directions of light emitted from thelaser light sources; and polarization directions of the light thatenters and is emitted from first retardation plate 24, secondretardation plate 26, polarization beam splitter 25, blue-reflectingdichroic mirror 31, red-reflecting dichroic mirror 36, and seconddichroic mirror 46. Specifically, in FIG. 1 , the fisheye marks indicateS-polarized light, the double-headed arrow marks indicate P-polarizedlight, and the upward, downward, leftward, and rightward arrows showntogether with the marks indicating the polarizations indicate travelingdirections of the polarized light.

Blue laser light source 22 includes: blue semiconductor laser substrate20 on which 24 (6×4) blue semiconductor laser elements aretwo-dimensionally arranged at regular intervals; and collimating lensarray 21. Blue semiconductor laser substrate 20 generates blue colorlight in a wavelength band of 455±8 nm and emits linearly polarizedlight. The light beams emitted from blue semiconductor laser substrate20 are individually condensed and converted into parallel light beams bycorresponding collimating lens array 21. Heat sink 23 cools bluesemiconductor laser substrate 20.

Green laser light source 29 includes: green semiconductor lasersubstrate 27 on which 24 (6×4) green semiconductor laser elements aretwo-dimensionally arranged at regular intervals; and collimating lensarray 28. Green semiconductor laser substrate 27 generates green colorlight in a wavelength band of 525±8 nm and emits linearly polarizedlight. The light beams emitted from green semiconductor laser substrate27 are individually condensed and converted into parallel light beams bycorresponding collimating lens array 28. Heat sink 30 cools greensemiconductor laser substrate 27.

Red laser light source 34 includes: red semiconductor laser substrate 32on which 24 (6×4) red semiconductor laser elements are two-dimensionallyarranged at regular intervals; and collimating lens array 33. Redsemiconductor laser substrate 32 generates red color light in awavelength band of 640±8 nm and emits linearly polarized light. Thelight beams emitted from red semiconductor laser substrate 32 areindividually condensed and converted into parallel light beams bycorresponding collimating lens array 33. Heat sink 35 cools redsemiconductor laser substrate 32.

First retardation plate 24 controls polarization of blue laser lightemitted from blue laser light source 22.

The blue laser light emitted from blue laser light source 22 isP-polarized and enters first retardation plate 24. First retardationplate 24 is a half-wavelength plate having a retardation of a halfwavelength near a central emission wavelength of blue laser light source22. When the P-polarization direction in the drawing is 0 degrees, firstretardation plate 24 is disposed with its optical axis oriented at 15.7degrees. On the basis of the angle of disposition of the optical axis,first retardation plate 24 converts the P-polarized light entering firstretardation plate 24, into light in which the proportions of aP-polarized light component and an S-polarized light component are about73% and about 27%. That is, the expression of “controls polarization ofblue laser light” means here “to convert P-polarization blue laser lightinto light having a P-polarized light component and an S-polarized lightcomponent”. Note that in the configuration of the present exemplaryembodiment, P-polarized light is converted into light having aP-polarized light component and an S-polarized light component, butanother configuration may be used in which S-polarized light isconverted into light having a P-polarized light component and anS-polarized light component. First retardation plate 24 is rotationallyadjustable, and the optical axis can be adjusted in the range of 0degrees to 45 degrees inclusive when the angle of 15.7 degrees is astandard. In this case, the proportions of the P-polarized lightcomponent and the S-polarized light component can be adjusted in therange from 100% and 0% to 0% and 100% inclusive. As described above,first retardation plate 24 is controlled by a motor (not illustrated)and rotationally adjusted so as to adjust the proportions of the twoorthogonal polarization components. First retardation plate 24 is a fineperiodic-structured retardation plate using birefringence caused in afine periodic structure smaller than a wavelength of light. The fineperiodic-structured retardation plate is made of an inorganic material.Similar to an inorganic optical crystal such as quartz, the fineperiodic-structured retardation plate has excellent durability andreliability, and is relatively low in cost. The blue laser lightcontaining a P-polarized light component and an S-polarized lightcomponent emitted from first retardation plate 24 enters flatplate-shaped polarization beam splitter 25. In other words, the bluelaser light whose polarization is controlled by first retardation plate24 enters polarization beam splitter 25.

Polarization beam splitter 25 separates the blue laser light whosepolarization is controlled by first retardation plate 24 into first bluelaser light and second blue laser light. The first blue laser light hereis the P-polarized light that is separated by polarization beam splitter25, and the second blue laser light here is the S-polarized light thatis separated by polarization beam splitter 25. Polarization beamsplitter 25 is an optical thin film formed on a glass substrate, andallows the P-polarized light of incident blue laser light to passthrough with a transmittance of 96% or more and reflects the S-polarizedlight of the incident blue laser light with a reflectance of 96% ormore. That is, the P-polarized light emitted from first retardationplate 24 passes through polarization beam splitter 25 as the first bluelaser light that is P-polarized light. The S-polarized light emittedfrom first retardation plate 24 is reflected by polarization beamsplitter 25, as the second blue laser light that is S-polarized light.

The S-polarized blue laser light reflected by polarization beam splitter25 enters second retardation plate 26. Second retardation plate 26controls the polarization of the second blue laser light, which isS-polarized light and is separated by polarization beam splitter 25.Second retardation plate 26 is a half-wavelength plate having aretardation of a half wavelength near a central emission wavelength ofblue laser light source 22. When the P-polarization direction in thedrawing is 0 degrees, second retardation plate 26 is disposed with itsoptical axis oriented at 45 degrees. Second retardation plate 26converts the S-polarized light entering second retardation plate 26 tothe P-polarization direction. That is, the second retardation plate is ahalf-wavelength plate that converts a polarization direction.Specifically, second retardation plate 26 converts the S-polarized bluelaser light reflected by polarization beam splitter 25 to theP-polarization direction.

Second retardation plate 26 is a fine periodic-structured retardationplate. The fine periodic-structured retardation plate is made of aninorganic material, has excellent durability and reliability, and isrelatively low in cost. The blue laser light emitted from secondretardation plate 26 enters blue-reflecting dichroic mirror 31, in theP-polarization state. That is, the second blue laser light whosepolarization is controlled by second retardation plate 26 entersblue-reflecting dichroic mirror 31. Further, P-polarized green laserlight emitted from green laser light source 29 enters blue-reflectingdichroic mirror 31. Blue-reflecting dichroic mirror 31 has the followingcharacteristics. When disposed such that the incident angles are 45degrees, blue-reflecting dichroic mirror 31 allows the green laser lightto pass through with a transmittance of 94% or more and reflects theblue laser light with a reflectance of 96% or more. The half-valuewavelength at which the transmittance is 50% is 490 nm for P-polarizedlight.

The blue laser light and the green laser light combined byblue-reflecting dichroic mirror 31 enter red-reflecting dichroic mirror36. P-polarized red laser light emitted from red laser light source 34enters red-reflecting dichroic mirror 36. Red-reflecting dichroic mirror36 has the following characteristics. When disposed such that theincident angles are 45 degrees, red-reflecting dichroic mirror 36 allowsthe blue laser light and the green laser light to pass through with atransmittance of 94% or more and reflects the red laser light with areflectance of 96% or more. The half-value wavelength at which thetransmittance is 50% is 583 nm for P-polarized light. Here, a pair ofblue-reflecting dichroic mirror 31 and red-reflecting dichroic mirror 36is a first dichroic mirror that combines blue, green, and red laserlights.

The blue, green, and red laser lights are combined by the first dichroicmirror. That is, the first dichroic mirror combines the second bluelaser light whose polarization is controlled by second retardation plate26, the green laser light emitted from green laser light source 29, andthe red laser light emitted from red laser light source 34. The blue,green, and red laser lights are condensed by condenser lens 37, and thenenter diffuser plate 38. A focal length of condenser lens 37 is set suchthat a converging angle is 30 degrees or smaller, and a converged spotis formed near rotary diffuser plate 42. Diffuser plate 38 has adiffusion surface configured with fine microlenses formed in an array ona glass substrate, and diffuses incident light. Since the diffusionsurface is made in a microlens shape, the maximum spread angle can bereduced as compared with a chemically treated diffuser plate in which aglass surface is processed to have fine irregularities by using asolution of hydrofluoric acid or the like, so that a diffusion loss canbe reduced. A diffusion angle, which is a half-value angular width atwhich the intensity is 50% of maximum intensity of diffused light, is assmall as approximately 3 degrees, and polarization characteristics aremaintained. The light diffused by diffuser plate 38 is reflected byreflecting mirror 39, and then enters rotary diffuser plate 42.

Rotary diffuser plate 42 diffuses the laser light combined by the firstdichroic mirror. Rotary diffuser plate 42 includes: a circular diffuserplate 40 having, on one surface of a glass substrate, a diffusion layerhaving fine irregularities formed in a circumferential shape; and motor41 in the central part of rotary diffuser plate 42, and the rotation ofrotary diffuser plate 42 can be rotationally controlled. The rotarydiffuser plate can be rotated at a high speed up to about 10,800 rpm. Asthe diffusion layer of circular diffuser plate 40, a chemically treateddiffuser plate whose diffusion angle is approximately 15 degrees isused, and polarization characteristics are maintained. When thechemically treated diffuser plate is employed, a large-sized diffuserplate can be manufactured at relatively low cost as compared with adiffuser plate with a microlens array. By rotating the diffusionsurface, a random interference pattern on a screen caused by laser lightvaries temporally and spatially at a high speed, so that speckle noiseis eliminated. In addition, it is possible to reduce minute luminanceunevenness due to a small emission size and a number of emissions ofeach laser light source. The light passing through rotary diffuser plate42 and being diffused is condensed by condenser lens 43, is convertedinto parallel light, and then enters second dichroic mirror 46.

On the other hand, the P-polarized blue laser light passing throughpolarization beam splitter 25 enters diffuser plate 44. Diffuser plate44 has a diffusion surface configured with fine microlenses formed on aglass substrate in an array, has a small diffusion angle ofapproximately 3 degrees, and maintains polarization characteristics. Thelight diffused by diffuser plate 44 enters blue transmission filter 45.Blue transmission filter 45 has the following characteristics. Whendisposed such that the incident angle is 0 degrees, the bluetransmission filter 45 has a half-value wavelength of 480 nm, at whichthe transmittance is 50%, allows the light in a wavelength band of theblue laser light to pass through with a transmittance of 96% or more,and reflect the light in the other wavelength band with a reflectance of98% or more. The P-polarized blue laser light passing through bluetransmission filter 45 enters second dichroic mirror 46.

FIG. 2 shows spectral transmittance characteristics of second dichroicmirror 46. FIG. 2 illustrates spectral transmittance characteristics ofP-polarized light and S-polarized light of second dichroic mirror 46.Second dichroic mirror 46 has characteristics that the transmittance ofP-polarized light is 90% or more for each of the wavelength bands of theblue laser light, the green laser light, and the red laser light. Inaddition, second dichroic mirror 46 has characteristics that thetransmittance is 10% or less for the S-polarized light in a wavelengthband of 485 nm to 700 nm including each of the wavelength bands of thegreen laser light and the red laser light. In other words, seconddichroic mirror 46 has the following characteristics. Each of the blue,green, and red laser lights of P-polarization passes through with atransmittance of 90% or more, each of the green and red laser lights ofS-polarization are reflected with a reflectance of 90% or more, andfluorescent light outside the wavelength bands of the blue, green, andred laser lights is reflected. The characteristics of FIG. 2 are anexample designed by alternately forming, on a glass substrate, 89 layersof optical thin films of high refractive index material such as TiO₂ anda low refractive material such as SiO₂.

Each of the blue, green, and red laser lights entering second dichroicmirror 46 from condenser lens 43 is P-polarized light, and passesthrough second dichroic mirror 46 with a transmittance of 90% or more.Each laser light passing through second dichroic mirror 46 is emittedfrom light source device 53 to become effective light.

The blue laser light entering second dichroic mirror 46 from bluetransmission filter 45 is P-polarized light, and passes through seconddichroic mirror 46 with a transmittance of 90% or more. The blue laserlight of P-polarization passing through second dichroic mirror 46 entersfluorescent plate 52 while being condensed by condenser lenses 47, 48and superposed to make a spot light with a spot diameter of 2 mm to 3 mmwhen the spot diameter is defined by a diameter at which light intensityis 13.5% of a peak intensity to enter fluorescent plate 52. Diffuserplate 44 diffuses the light such that the diameter of the spot light isa desired diameter.

Fluorescent plate 52 is a rotation-controllable circular substrateincluding: aluminum substrate 50 on which a reflection film and phosphorlayer 49 are formed; and motor 51 in the central part. The reflectionfilm of fluorescent plate 52 is a metal film or a dielectric film thatreflects visible light, and reflection film of fluorescent plate 52 isformed on aluminum substrate 50. Further, phosphor layer 49 is formed onthe reflection film.

Phosphor layer 49 is made of a Ce:YAG based yellow phosphor that isexcited by blue light and emits yellow light containing green and redcomponents. A typical chemical composition of a crystalline matrix ofthis fluorescent material is Y₃Al₅O₁₂. Phosphor layer 49 is formed in anannular shape. When excited by the spot light, phosphor layer 49 emitsyellow light containing green and red components. Fluorescent plate 52has aluminum substrate 50 and is rotated. The rotation reduces atemperature rise of phosphor layer 49 caused by blue laser light that isthe excitation light, thereby stably maintaining fluorescence conversionefficiency. The blue laser light entering phosphor layer 49 excitesphosphor layer 49. Excited phosphor layer 49 generates a color lightincluding green and red components. Then, the color light including thegreen and red components is emitted from fluorescent plate 52. Further,the light generated toward a reflection film side is reflected by thereflection film and is emitted from fluorescent plate 52. The colorlight emitted from fluorescent plate 52 and including the green and redcomponents becomes randomly polarized light, is condensed again andconverted into approximately parallel light by condenser lenses 47, 48,and then enters second dichroic mirror 46. Here, the color lightincluding the green and red components is referred to as a fluorescentlight.

FIG. 3 is a diagram showing fluorescence spectrum characteristics of thefluorescent light. FIG. 3 illustrates a relative light intensity of thefluorescent light with respect to the wavelength. The fluorescent lightis yellow light having a peak at 544 nm.

The P-polarized light component of the fluorescent light entering seconddichroic mirror 46 passes through second dichroic mirror 46 with atransmittance of 90% or more in each of the wavelength bands of thegreen laser light and the red laser light, but the light in the otherwavelength band is reflected with a reflectance of 90% or more. TheS-polarized light component of the fluorescent light entering seconddichroic mirror 46 is reflected with a reflectance of 90% or more. Thefluorescent light reflected by second dichroic mirror 46 is emitted fromlight source device 53 to become effective light.

The P-polarized light component of the fluorescent light passing throughsecond dichroic mirror 46 is reflected by blue transmission filter 45,passes again through second dichroic mirror 46, and is condensed onfluorescent plate 52 by condenser lenses 47, 48. The fluorescent lightof P-polarization entering fluorescent plate 52 is scattered by phosphorlayer 49 and reflection layer; therefore, the fluorescent light becomesrandomly polarized light and is emitted from fluorescent plate 52. Thefluorescent light emitted from fluorescent plate 52 is condensed bycondenser lenses 47, 48, and then enters second dichroic mirror 46, andthe P-polarized light component of each of the wavelength bands of thegreen laser light and the red laser light passes through second dichroicmirror 46, and the S-polarized light component of each wavelength bandis reflected. In this manner, part of the fluorescent light of theP-polarized light component passing through second dichroic mirror 46 isreflected by blue transmission filter 45 and is converted into randomlypolarized light by the fluorescent plate 52. Therefore, the light thatpasses through second dichroic mirror 46 and would be lost can beconverted into effective light that is reflected by second dichroicmirror 46. Due to repeated reflection between blue transmission filter45 and fluorescent plate 52, part of the P-polarized fluorescent lightis converted into effective S-polarized fluorescent light. In this case,a light flux emitted from the light source device is improved by about8% as compared with the case where blue transmission filter 45 is notdisposed.

The blue, green, and red laser lights and the fluorescent light arecombined on the same optical axis by second dichroic mirror 46 and bluetransmission filter 45 with an efficiency of 90% or more for the laserlight and with an efficiency about 93% for the fluorescent light withrespect to fluorescent spectrum, and as a result, white light isemitted. The light flux of the blue, green, and red laser lights emittedfrom light source device 53 and the light flux of the fluorescent lightare made substantially equal to each other. In this case, the colorgamut roughly encompasses the color gamut standard DCI (Digital CinemaInitiatives).

By controlling the light output of each laser light source by a drivecurrent and by controlling the blue excitation light intensity byadjusting the inclination of the optical axis of first retardation plate24, it is possible to control the intensity proportions of the laserlight and the fluorescent light and to control the white balance.Therefore, it is possible to adjust the color gamut from the color gamutstandard Rec709 in the case of reducing the output of the green and redlaser lights, to the color gamut standard DCI in the case of equalizingthe light flux of the laser lights and the light flux of the fluorescentlight, and to the color gamut standard Rec2020 in the case of reducingthe output of the fluorescent light.

The blue, green, and red laser lights emitted from second dichroicmirror 46 are combined with the fluorescent light having no specklenoise. Therefore, the light emitted from light source device 53 is lightwhich has a wide color gamut and in which speckle noise is eliminated.

In the described configuration of each of the green laser light source,the red laser light source, and the blue laser light source, 24semiconductor laser elements are arranged; however, the laser lightsources may be configured with more semiconductor laser elements forhigher luminance.

The first retardation plate may be a quarter-wavelength plate in thecase where the control ratio between the P-polarized light component andthe S-polarized light component may be in the range from 100% and 0% to50% and 50% inclusive.

As the dynamic diffuser plate, the rotary diffuser plate is described,but it is possible to use a moving diffuser plate whose diffusionsurface is moved.

As described above, in the light source device of the presentdisclosure, since the blue projection light and the blue laserexcitation light whose intensities can be controlled are obtained fromthe same blue laser light source by using the retardation plate and thepolarizing beam splitter, it is possible to downsize the blue laserlight source. In addition, color gamut adjustment can be performed bydimming with the laser light sources and the retardation plate. Further,the second dichroic mirror efficiently combines, on the same opticalaxis, the light of blue, green, and red laser light sources andfluorescent light having no speckle noise. Therefore, a small-sizedlight source device can be configured which has a wide and adjustablecolor gamut and in which speckle noise and minute luminance unevennessare eliminated.

Second Exemplary Embodiment

FIG. 4 illustrates first projection-type display apparatus 150 accordingto a second exemplary embodiment of the present disclosure. Firstprojection-type display apparatus 150 uses three display digitalmicromirror devices (DMDs) as an image former. A light source device offirst projection-type display apparatus 150 is light source device 53described in the first exemplary embodiment of the present disclosure.First projection-type display apparatus 150 includes condenser lens 100,rod 101, relay lens 102, reflecting mirror 103, field lens 104, totalreflection prism 105, air layer 106, color prism 107 including threeprisms provided with blue-reflecting dichroic mirror 108 andred-reflecting dichroic mirror 109, DMDs 110, 111, 112, and projectionlens 113. Here, DMDs 110, 111, 112 are each an example of a pixelforming element.

The combined light containing the laser light and the fluorescent lightemitted from light source device 53 is condensed on rod 101 by condenserlens 100. The light entering rod 101 is reflected a plurality of timesinside the rod so that the light intensity is homogenized, and is thenemitted from rod 101. The light emitted from rod 101 is condensed byrelay lens 102, is reflected by reflecting mirror 103, passes throughfield lens 104, and enters total reflection prism 105. Total reflectionprism 105 includes two prisms, and thin air layer 106 is formed betweensurfaces of the prisms close to each other. Air layer 106 totallyreflects light entering at an angle greater than or equal to a criticalangle. The light passing through field lens 104 is reflected by a totalreflection surface of total reflection prism 105 and enters color prism107. Color prism 107 is configured with three prisms, andblue-reflecting dichroic mirror 108 and red-reflecting dichroic mirror109 are formed on surfaces on which the prisms are adjacent to eachother. Light entering color prism 107 is separated into color lights ofblue, red, and green by blue-reflecting dichroic mirror 108 andred-reflecting dichroic mirror 109 of color prism 107, and the blue,red, and green color lights respectively enter DMDs 110, 111, 112. DMDs110, 111, 112 each deflect micromirrors in accordance with a videosignal and reflects the light as the two lights: the light enteringprojection lens 113; and the light traveling outside an effective areaof projection lens 113. That is, DMDs 110, 111, 112 are each an imageforming element that forms an image in accordance with a video signal.In each of DMDs 110, 111, 112, a region on which the micromirrors arearranged and which reflects light is an example of an area to beilluminated. Condenser lens 100, rod 101, relay lens 102, reflectingmirror 103, and field lens 104 are an example of an illumination opticalsystem that condenses the light emitted from the light source device andilluminates the area to be illuminated.

The light reflected by DMDs 110, 111, 112 passes through color prism 107again. In the course of passing through color prism 107, the separatedblue color light, red color light, and green color light are combinedand enter total reflection prism 105. Because the light entering totalreflection prism 105 enters air layer 106 at the critical angle or less,the light passes through air layer 106 to enter projection lens 113. Inthis manner, image light formed by DMDs 110, 111, 112 is enlarged andprojected on a screen (not illustrated).

The light flux from the blue, green, and red laser light sources and thelight flux from the fluorescent plate are made approximately equal toeach other. The color gamut roughly encompasses the color gamut standardDCI.

By controlling the light output of each laser light source by means of adrive current and by controlling the excitation light intensity byadjusting the inclination of the optical axis of first retardation plate24, it is possible to control the intensity proportions of the laserlight and the fluorescence and to control the white balance. Therefore,it is possible to adjust the color gamut from the color gamut standardRec709 in the case of reducing the output of the green and red laserlights, to the color gamut standard DCI in the case of equalizing thelight flux of the laser lights and the light flux of the fluorescentlight, and to the color gamut standard Rec2020 in the case of reducingthe output of the fluorescent light.

Since DMDs are used for an image former, a projection-type displayapparatus can be configured which has higher light resistance and heatresistance as compared with an apparatus provided with an image formerusing liquid crystal. Further, since three DMDs are used, a bright andhigh-definition projection image with good color reproduction can beobtained.

As described above, first projection-type display apparatus 150 of thepresent disclosure uses light source device 53 according to the firstexemplary embodiment of the present disclosure. Therefore, a small-sizedprojection-type display apparatus can be configured which has a wide andadjustable color gamut and in which speckle noise and minute luminanceunevenness are eliminated.

Third Exemplary Embodiment

FIG. 5 illustrates second projection-type display apparatus 250according to a third exemplary embodiment of the present disclosure.Second projection-type display apparatus 250 uses, as an image former,an active matrix-type transmissive liquid crystal panel of a TN mode ora VA mode in which thin film transistors are formed in a pixel area. Thelight source device of second projection-type display apparatus 250 islight source device 53 described in the first exemplary embodiment ofthe present disclosure. Second projection-type display apparatus 250includes first lens array plate 200, second lens array plate 201,polarization conversion element 202, superposition lens 203,blue-reflecting dichroic mirror 204, green-reflecting dichroic mirror205, reflecting mirrors 206, 207, 208, relay lenses 209, 210, fieldlenses 211, 212, 213, incidence-side polarizing plates 214, 215, 216,liquid crystal panels 217, 218, 219, exit-side polarizing plates 220,221, 222, color-combining prism 223 configured with a red-reflectingdichroic mirror and a blue-reflecting dichroic mirror, and projectionlens 224. Here, the pixel area of the liquid crystal panel is an exampleof an area to be illuminated, and first lens array plate 200, secondlens array plate 201, polarization conversion element 202, andsuperposition lens 203 are an example of an illumination optical systemthat condenses the light emitted from light source device 53 andilluminates the area to be illuminated.

The combined light of the laser light and the fluorescent light emittedfrom light source device 53 enters first lens array plate 200 includinga plurality of lens elements. The light flux of the combined lightentering first lens array plate 200 is divided into a large number oflight fluxes. The large number of divided light fluxes are converged onsecond lens array plate 201 including a plurality of lenses. The lenselements of first lens array plate 200 have an aperture shape similar tothe aperture shape of liquid crystal panels 217, 218, 219. Regarding thelens elements of second lens array plate 201, the focal length isdetermined such that first lens array plate 200 and liquid crystalpanels 217, 218, 219 are in an approximate conjugate relation. Thedivided light beams emitted from second lens array plate 201 enterpolarization conversion element 202. Polarization conversion element 202includes a polarization separation prism and a half-wavelength plate.Polarization conversion element 202 converts the incident P-polarizedlight and randomly polarized light into S-polarized light, and allowsthe incident S-polarized light to exit as S-polarized light. The lightemitted from polarization conversion element 202 enters superpositionlens 203. Superposition lens 203 superposes the light emitted from eachof lens element of second lens array plate 201 on liquid crystal panels217, 218, 219 to illuminate. First lens array plate 200, second lensarray plate 201, and superposition lens 203 are used as an illuminationoptical system. The light emitted from superposition lens 203 isseparated into blue, green, and red color lights by blue-reflectingdichroic mirror 204 and green-reflecting dichroic mirror 205 that serveas a color separator. The green color light passes through field lens211 and incidence-side polarizing plate 214, and then enters liquidcrystal panel 217. The blue color light is reflected by reflectingmirror 206, and then passes through field lens 212 and incidence-sidepolarizing plate 215, and enters liquid crystal panel 218. After passingthrough relay lenses 209, 210 and being reflected by reflecting mirrors207, 208, the red color light passes through field lens 213 andincidence-side polarizing plate 216, and then enters liquid crystalpanel 219. Three liquid crystal panels 217, 218, 219 each change thepolarization state of incident light by controlling voltages applied tothe pixels, depending on a video signal. Further, the light is modulatedby combining incidence-side polarizing plates 214, 215, 216 andexit-side polarizing plates 220, 221, 222 respectively disposed on bothsides of liquid crystal panels 217, 218, 219 such that transmission axesare orthogonal to each other between the both sides, so that green,blue, and red images are formed. Regarding the color lights passingthrough exit-side polarizing plates 220, 221, 222, color-combining prism223 causes the red light and the blue light to be reflected respectivelyby a red-reflecting dichroic mirror and a blue-reflecting dichroicmirror, and the red color light and the blue color light are combinedwith the green color light, and then, the combined light entersprojection lens 224. The light entering projection lens 224 (an imageformed by the liquid crystal panels) is enlarged and projected on ascreen (not illustrated).

The light fluxes emitted from the blue, green, and red laser lightsources and the light flux emitted from the fluorescent plate are madeapproximately equal to each other. The color gamut roughly encompassesthe color gamut standard DCI.

By controlling the light output of each laser light source by means of adrive current and by controlling the excitation light intensity byadjusting the inclination of the optical axis of first retardation plate24, it is possible to control the intensity proportions of the laserlight and the fluorescence and to control the white balance. Therefore,it is possible to adjust the color gamut from the color gamut standardRec709 in the case of reducing the output of the green and red laserlights, to the color gamut standard DCI in the case of equalizing thelight flux of the laser lights and the light flux of the fluorescentlight, and to the color gamut standard Rec2020 in the case of reducingthe output of the fluorescent light.

As the image former, three liquid crystal panels using polarization areused instead of the time-division system, it is possible to obtain abright and high-definition projection image with excellent colorreproduction without color breaking. In addition, because a totalreflection prism is not necessary, a small prism having a 45 degreesincident angle can be used as the color-combining prism, so that theprojection-type display apparatus can be downsized as compared with anapparatus using three DMD elements.

As described above, second projection-type display apparatus 250 of thepresent disclosure uses light source device 53 according to the firstexemplary embodiment of the present disclosure. Therefore, a small-sizedprojection-type display apparatus can be configured which has a wide andadjustable color gamut and in which speckle noise and minute luminanceunevenness are eliminated.

Although transmissive liquid crystal panels are used as the imageformer, reflective liquid crystal panels may be used. By usingreflective liquid crystal panels, a more small-sized andhigher-definition projection-type display apparatus can be configured.

INDUSTRIAL APPLICABILITY

The present disclosure relates to a light source device for aprojection-type display apparatus using an image former.

The invention claimed is:
 1. A light source device comprising: a bluelaser light source; a green laser light source; a red laser lightsource; a first retardation plate that controls polarization of bluelaser light emitted from the blue laser light source; a polarizing beamsplitter that separates the blue laser light whose polarization iscontrolled by the first retardation plate into a first blue laser lightand a second blue laser light; a second retardation plate that controlspolarization of the second blue laser light separated by the polarizingbeam splitter; a fluorescent plate that is excited by the first bluelaser light separated by the polarizing beam splitter and emitsfluorescent light including a green component and a red component; afirst dichroic mirror that combines the second blue laser light whosepolarization is controlled by the second retardation plate, green laserlight emitted from the green laser light source, and red laser lightemitted from the red laser light source, to generate combined laserlight; a dynamic diffuser plate that diffuses the combined laser lightcombined by the first dichroic mirror to generate diffused laser light;and a second dichroic mirror that combines the diffused laser lightdiffused by the dynamic diffuser plate and the fluorescent light emittedfrom the fluorescent plate.
 2. The light source device according toclaim 1, wherein the first retardation plate is a half-wavelength plate.3. The light source device according to claim 1, wherein the firstretardation plate is rotationally adjusted to adjust a ratio between twopolarization components orthogonal to each other.
 4. The light sourcedevice according to claim 1, wherein the polarizing beam splitter is aflat plate-shaped polarization beam splitter.
 5. The light source deviceaccording to claim 1, wherein the second retardation plate is ahalf-wavelength plate that converts a polarization direction.
 6. Thelight source device according to claim 1, wherein the dynamic diffuserplate is a rotary diffuser plate that includes: a circular diffuserplate including a glass substrate, a surface of the glass substratehaving fine irregularities formed in a circumferential shape; and amotor.
 7. The light source device according to claim 1, wherein thefluorescent plate is a rotation-controllable circular substrate, andincludes a phosphor layer formed of a Ce:YAG based yellow phosphor. 8.The light source device according to claim 1, wherein the seconddichroic mirror allows the blue laser light, the green laser light, andthe red laser light that are P-polarized to pass through with atransmittance of 90% or more, reflects the green laser light and the redlaser light that are S-polarized with a reflectance of 90% or more, andreflects the fluorescent light outside wavelength bands of the bluelaser light, the green laser light, and the red laser light.
 9. Thelight source device according to claim 1, further comprising, betweenthe polarizing beam splitter and the second dichroic mirror, a bluetransmission filter that allows the blue laser light to pass through andreflects the fluorescent light.
 10. The light source device according toclaim 1, wherein the blue laser light source, the green laser lightsource, and the red laser light source are semiconductor lasers.
 11. Aprojection-type display apparatus comprising: a light source; anillumination optical system that condenses light emitted from the lightsource and illuminates an area to be illuminated; an image formingelement that forms an image, based on a video signal; and a projectionlens that enlarges and projects the image formed by the image formingelement, wherein the light source is the light source device accordingto claim
 1. 12. The projection-type display apparatus according to claim11, wherein the image forming element is a liquid crystal panel.
 13. Theprojection-type display apparatus according to claim 11, wherein theimage forming element is a mirror-deflection-type digital micromirrordevice (DMD).